Many static random access memories (SRAMS) utilize polysilicon load resistors. In other words, each basic SRAM cell contains two access transistors, two pull-down transistors, and two polysilicon load resistors. Such SRAM cells typically contain at least two, usually three levels of polysilicon runners.
Those concerned with SRAM development have noticed that mobile charge in the vicinity of the polysilicon resistor tends to degrade cell performance. Attempts to solve the problem have included the placement of layers made from doped TEOS (i.e., in BPTEOS) at a substantially upper level i.e., near the third polysilicon level of the integrated circuit. However, experiments have shown that the problem has still not been solved.
Another dielectric material sometimes utilized as a sodium getter is phosphorus-doped glass or p-glass. Phosphorus-doped glass has been occasionally utilized in integrated circuits which use aluminum metallization. Typically, the phosphorus-doped glass is either: (a) not heated after formation, or (b) heated to a high temperature such as 900.degree. to 1000.degree. C. to cause flow after formation.
Those concerned with the development of integrated circuits, particularly SRAMS, or other devices with multiple levels of patterned conductors have continued to search for structures and methods to alleviate mobile ion contamination.